1. Field
The present invention relates to a semiconductor device and a method for manufacturing the same.
2. Description of Related Art
Recently, in order to reduce resistance of conductor plugs and interconnect lines, the use of copper (Cu) as a material for conductor plugs and interconnect lines has been receiving attention.
A Cu film is a material that is difficult to dry etch. Therefore, a method is employed in which contact holes and trenches are formed in an interlayer insulation film, a Cu film is formed on the interlayer insulation film provided with the contact holes and the trenches, and then, by polishing the Cu film until the surface of the interlayer insulation film is exposed, the Cu film is embedded into the contacts holes and the trenches. Such a method of embedding a Cu film into contact holes and trenches is referred to as a damascene process or a dual damascene process.
When conductor plugs and interconnect lines composed of Cu are directly in contact with an interlayer insulation film, Cu atoms in the conductor plugs and the interconnect lines diffuse into the interlayer insulation film, giving rise to problems, such as short-circuiting. Consequently, a barrier film for preventing the diffusion of Cu atoms is disposed in the contact holes and the trenches. As the material for the barrier film, for example, Ta is used.
Recently, in order to achieve further miniaturization of semiconductor devices, it has been required to significantly reduce the diameter of contact holes in which conductor plugs are to be embedded and the width of trenches in which interconnect lines are to be embedded. In order to significantly reduce the diameter of contact holes, it is necessary to significantly decrease the thickness of a barrier film. On the other hand, in order to increase the speed of semiconductor devices, it has been required to decrease the capacitance between interconnect lines. Recently, as an insulation film that can decrease the capacitance between interconnect lines, a low-dielectric-constant film composed of a porous material has been proposed.
However, when the thickness of a barrier film composed of Ta or the like is significantly decreased, the barrier properties of the barrier film are degraded. In particular, large amounts of moisture and oxygen gas are released from an interlayer insulation film composed of a porous material. Consequently, when such an interlayer insulation film composed of a porous material is used, the barrier film is significantly degraded by moisture, oxygen gas, etc.